Soil quality indices based on long-term conservation cropping systems management

Abstract

The Soil Management Assessment Framework (SMAF) may provide insight into how conservation practices affect soil quality (SQ) regionally. Therefore, we aimed to quantify SQ in a long-term (15-yr) crop rotation and bio-covers experiment under no-tillage using SMAF. Main effects were cropping rotations of soybean [Glycine max (L.) Merr.], corn (Zea mays L.), and cotton (Gossypium hirsutum L.). Split-block bio-cover treatments consisted of winter wheat (Triticum aestivum L.), Austrian winter pea (Pisum sativum L. sativum var. arvense), hairy vetch (Vicia villosa Roth), poultry litter, and fallow (control). Seven SQ indicators—soil pH, total organic carbon (TOC), bulk density (BD), soil extractable P and K, electrical conductivity (EC), and sodium adsorption ration (SAR)—were scored using SMAF algorithms, and investigated individually and as an overall soil quality index (SQI). Simple linear regressions were performed between SQI and crop yields. Differences (p < .05) in SQI within rotations varied when analyzed across and by depth. Overall, cotton–corn and/or continuous corn had greater SQI than soybean-based rotations. Poultry litter had the greatest TOC, pH, K, and BD scores at the 0- to 15-cm soil depth, and the lowest SQI. Reductions in SQI within bio-covers were linked to P scores. A positive relationship was found between SQI and cotton yield at the 15- to 30-cm soil depth (R2 = .48; p < .05). Investigating SMAF scores individually and separately per depth addresses the effects of long-term conservation practices on SQ. Overall, SMAF can be used to develop best management practices and nutrient management strategies.